Kinetics Of Electrode Reactions Research Articles

Boosted Polysulfide Conversion by Co, Mn Bimetallic-Modulated Nitrogen–Carbon Material for Advanced Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are regarded as one of the most promising future generation rechargeable battery energy storage devices due to their high theoretical specific capacity and energy density. However, the development of LSBs is largely influenced by the shuttle effect and slow kinetics of lithium polysulfides, which seriously hinder their commercial applications. Based on this, we propose a bimetallic modulating strategy to synthesize carbon tube embedded with Co and Mn bimetals anchored on a nitrogen-doped carbon nanosheet (Co/Mn-GC@N–C) function separator to catalytic polysulfide conversion and enhance the electrochemical performance. Co/Mn-GC@N–C possesses high electrical conductivity and large specific surface area, which can offer a lot of active sites for anchoring polysulfides, stimulating their redox reaction and quickening the electrode reaction kinetics. The comprehensive test results show that the cell with Co/Mn-GC@N–C exhibits a specific discharge capacity of 1215 mAh g–1 at 0.5C and a high Coulombic efficiency of 99.4% after 300 cycles; even the Co/Mn-GC@N–C cell with a high sulfur loading of 6.6 mg cm–2 shows a high area capacity of 5 mAh cm–2. Therefore, this bimetallic modulating strategy provides an option for the design of advanced high-performance lithium–sulfur battery separator materials.

Synthesis and Characterization of Dense Carbon Films as Model Surfaces to Estimate Electron Transfer Kinetics on Redox Flow Battery Electrodes.

Redox flow batteries (RFBs) are a promising electrochemical technology for the efficient and reliable delivery of electricity, providing opportunities to integrate intermittent renewable resources and to support unreliable and/or aging grid infrastructure. Within the RFB, porous carbonaceous electrodes facilitate the electrochemical reactions, distribute the flowing electrolyte, and conduct electrons. Understanding electrode reaction kinetics is crucial for improving RFB performance and lowering costs. However, assessing reaction kinetics on porous electrodes is challenging as their complex structure frustrates canonical electroanalytical techniques used to quantify performance descriptors. Here, we outline a strategy to estimate electron transfer kinetics on planar electrode materials of similar surface chemistry to those used in RFBs. First, we describe a bottom-up synthetic process to produce flat, dense carbon films to enable the evaluation of electron transfer kinetics using traditional electrochemical approaches. Next, we characterize the physicochemical properties of the films using a suite of spectroscopic methods, confirming that their surface characteristics align with those of widely used porous electrodes. Last, we study the electrochemical performance of the films in a custom-designed cell architecture, extracting intrinsic heterogeneous kinetic rate constants for two iron-based redox couples in aqueous electrolytes using standard electrochemical methods (i.e., cyclic voltammetry, electrochemical impedance, and spectroscopy). We anticipate that the synthetic methods and experimental protocols described here are applicable to a range of electrocatalysts and redox couples.

Effect of Ti doping on the structure and electrochemical properties of Na3V2(PO4)2F3 as anode material for sodium ion batteries

In this article, Co-doped Na3V2- x Ti x (PO4)2F3(NVTPF x = 0, 0.1, 0.5, 0.7) sodium ion battery anode material was prepared by one-step hydrothermal method and it was coated with graphene. The crystal structure and morphology of NVTPF cathode material were characterized by scanning electron microscope and X-ray diffractometer. The results show that the particle diameter of the sample becomes smaller and the shape gradually becomes regular with the increase of Ti doping amount. The graphene coating did not change the crystal structure of NVTPF, but it was helpful to improve its electrochemical performance. The substitution of Ti4+ for V3+ contributes to improve the electronic conductivity and diffusion coefficient of sodium ions, reduce the charge transfer impedance, and accelerate the reaction kinetics of NVTPF electrode, thus significantly improving the cycling stability of NVTPF electrode. Among the four groups of materials, Na3v1.5Ti0.5(PO4)2F3 has the best electrochemical performance. At 1C, the specific capacity of initial discharge is 53.4 mAh/g, and the capacity retention rate of 35 cycles is 72.3%. The graphene coated NVTPF has a discharge capacity of 125.9mAh/g for the first cycle and 44.8mAh/g for 35 cycles at 1C.

Physicochemical properties of different crystal forms of manganese dioxide prepared by a liquid phase method and their quantitative evaluation in capacitor and battery materials.

Although there are many studies on the preparation and electrochemical properties of the different crystal forms of manganese dioxide, there are few studies on their preparation by a liquid phase method and the influence of their physical and chemical properties on their electrochemical performance. In this paper, five crystal forms of manganese dioxide were prepared by using manganese sulfate as a manganese source and the difference of their physical and chemical properties was studied by phase morphology, specific surface area, pore size, pore volume, particle size and surface structure. The different crystal forms of manganese dioxide were prepared as electrode materials, and their specific capacitance composition was obtained by performing CV and EIS in a three-electrode system, introducing kinetic calculation and analyzing the principle of electrolyte ions in the electrode reaction process. The results show that δ-MnO2 has the largest specific capacitance due to its layered crystal structure, large specific surface area, abundant structural oxygen vacancies and interlayer bound water, and its capacity is mainly controlled by capacitance. Although the tunnel of the γ-MnO2 crystal structure is small, its large specific surface area, large pore volume and small particle size make it have a specific capacitance that is only inferior to δ-MnO2, and the diffusion contribution in the capacity accounts for nearly half, indicating it also has the characteristics of battery materials. α-MnO2 has a larger crystal tunnel structure, but its capacity is lower due to the smaller specific surface area and less structural oxygen vacancies. ε-MnO2 has a lower specific capacitance is not only the same disadvantage as α-MnO2, but also the disorder of its crystal structure. The tunnel size of β-MnO2 is not conducive to the interpenetration of electrolyte ions, but its high oxygen vacancy concentration makes its contribution of capacitance control obvious. EIS data shows that δ-MnO2 has the smallest charge transfer impedance and bulk diffusion impedance, while the two impedances of γ-MnO2 were the largest, which shows that its capacity performance has great potential for improvement. Combined with the calculation of electrode reaction kinetics and the performance test of five crystal capacitors and batteries, it is shown that δ-MnO2 is more suitable for capacitors and γ-MnO2 is more suitable for batteries.

Defect engineering of two-dimensional materials for advanced energy conversion and storage.

In the global trend towards carbon neutrality, sustainable energy conversion and storage technologies are of vital significance to tackle the energy crisis and climate change. However, traditional electrode materials gradually reach their property limits. Two-dimensional (2D) materials featuring large aspect ratios and tunable surface properties exhibit tremendous potential for improving the performance of energy conversion and storage devices. To rationally control the physical and chemical properties for specific applications, defect engineering of 2D materials has been investigated extensively, and is becoming a versatile strategy to promote the electrode reaction kinetics. Simultaneously, exploring the in-depth mechanisms underlying defect action in electrode reactions is crucial to provide profound insight into structure tailoring and property optimization. In this review, we highlight the cutting-edge advances in defect engineering in 2D materials as well as their considerable effects in energy-related applications. Moreover, the confronting challenges and promising directions are discussed for the development of advanced energy conversion and storage systems.

Boosting the Electrode Reaction Kinetics of SSOFCs by the Synergistic Effect of Nanoparticle Codecoration on Both the Cathode and Anode

A novel (SmBa)0.9Mn1.8Co0.2O5+δ (SBMCo) electrode is elaborately designed for symmetrical solid oxide fuel cells (SSOFCs). In operating conditions, the SBMCo material is codecorated with exsolved metallic cobalt for the anode and cobalt oxide for the cathode. The electrochemical impedance spectroscopy (EIS) results combined with distribution of relaxation times (DRT) analysis reveal that the rate-limiting step for hydrogen oxidation at the anode is the adsorbed hydrogen dissociation process, while for the oxygen reduction at the cathode, it is the charge transfer process. The exsolved nanoparticles on the SBMCo backbone of Co and Co3O4 significantly promote the corresponding rate-limiting steps and enable the decorated electrodes to exhibit remarkable catalytic activity toward hydrogen oxidation and oxygen reduction, respectively. When fueled with humidified hydrogen, the constructed symmetrical cell based on the designed SBMCo electrodes with the 300 μm La0.8Sr0.2Ga0.8Mg0.2O3−δ (LSGM) electrolyte-supported configuration delivers an attractive maximum power density of 712 mW cm–2 at 900 °C. The results demonstrate that the elaborate design of the codecorated anode and cathode from a single parent compound is a promising route for the development of candidate electrodes for SSOFCs.

Ni/NiO Exsolved Perovskite La0.2Sr0.7Ti0.9Ni0.1O3−δ for Semiconductor-Ionic Fuel Cells: Roles of Electrocatalytic Activity and Physical Junctions

A semiconductor-ionic fuel cell (SIFC) is recognized as a promising technology and an alternative approach to reduce the operating temperature of solid oxide fuel cells. The development of alternative semiconductors substituting easily reduced transition metal oxide is a great challenge as high activity and durability should be satisfied simultaneously. In this study, the B-site Ni-doped La0.2Sr0.7Ti0.9Ni0.1O3-δ (LSTN) perovskite is synthesized and used as a potential semiconductor for SIFC. The in situ exsolution and A-site deficiency strategy enable the homogeneous decoration of Ni/NiO nanoparticles as reactive sites to improve the electrode reaction kinetics. It also supports the formation of basic ingredient of the Schottky junction to improve the charge separation efficiency. Furthermore, additional symmetric Ni0.8Co0.15Al0.05LiO2-δ (NCAL) electrocatalytic electrode layers significantly enhance the electrode reaction activity and cells' charge separation efficiency, as confirmed by the superior open circuit voltage of 1.13 V (close to Nernst's theoretical value) and peak power density of 650 mW cm-2 at 550 °C, where the latter is one order of magnitude higher than NCAL electrode-free SIFC. Additionally, a bulk heterojunction effect is proposed to illustrate the electron-blocking and ion-promoting processes of the semiconductor-ionic composite electrolyte in SIFCs, based on the energy band values of the applied materials. Overall, we found that the energy conversion efficiency of novel SIFC can be remarkably improved through in situ exsolution and intentional introduction of the catalytic functionality.

Adjusting the 3d Orbital Occupation of Ti in Ti3C2 MXene via Nitrogen Doping to Boost Oxygen Electrode Reactions in Li–O2 Battery

Rationally designing efficient catalysts is the key to promote the kinetics of oxygen electrode reactions in lithium-oxygen (Li-O2 ) battery. Herein, nitrogen-doped Ti3 C2 MXene prepared via hydrothermal method (N-Ti3 C2 (H)) is studied as the efficient Li-O2 battery catalyst. The nitrogen doping increases the disorder degree of N-Ti3 C2 (H) and provides abundant active sites, which is conducive to the uniform formation and decomposition of discharge product Li2 O2 . Besides, density functional theory calculations confirm that the introduction of nitrogen can effectively modulate the 3d orbital occupation of Ti in N-Ti3 C2 (H), promote the electron exchange between Ti 3d orbital and O 2p orbital, and accelerate oxygen electrode reactions. Specifically, the N-Ti3 C2 (H) based Li-O2 battery delivers large discharge capacity (11679.8mAh g-1 ) and extended stability (372 cycles). This work provides a valuable strategy for regulating 3d orbital occupancy of transition metal in MXene to improve the catalytic activity of oxygen electrode reactions in Li-O2 battery.

Carbon doping switching on the fast reaction kinetics of advanced LiVO3 for lithium ion battery

LiVO3 has been recognized as a promising anode material for lithium storage because of its superior ion transfer capability and high theoretical capacity (1265 mAh g−1). However, its low electrical conductivity and hysteresis of the reaction kinetics limit the improvement of its electrochemical performance. In this work, carbon-doped LiVO3 nanofibers (C-doped LiVO3 NFs) are firstly designed and prepared via a simple and scalable electrospinning technique. The as-obtained C-doped LiVO3 NFs deliver high discharge capacity (913.7 mAh g−1 after 500 cycles at 0.2 A g−1) with obvious rise in capacity upon cycling, owing to its self-adaptive reaction kinetics. Moreover, the C-doped LiVO3 NFs electrode retains a high average discharge capacity of 676.2 mAh g−1 at 6.0 A g−1 and resumes the reversible capacity of 1137.5 mAh g−1 when the current returns to 0.2 A g−1 after 7 periodic rate performance tests. Surprisingly, the C-doped LiVO3 NFs anode exhibits an unprecedented long cycling performance with the capacity remaining at 560.3 mAh g−1 after 4200 cycles at the discharge current density of 4.0 A g−1. The above outstanding comprehensive electrochemical performance is attributed to rapid ion and electron transport triggered by carbon doping and the adaptive reaction kinetics of the C-doped LiVO3 NFs electrode, which is manifested in the gradually decreasing charge transfer impedance and the gradually increasing pseudocapacitance contribution upon cycling.

Revealing the accelerated reaction kinetic of Ni-rich cathodes by activated carbons for high performance lithium-ion batteries

Activated carbons (AC) play a key role in enabling the reaction kinetic of cathodes in lithium ion batteries (LIBs). However, the charge transfer dynamics and reaction kinetics mechanism of AC composited cathodes along their thickness direction are still poorly understood. Herein, we systematically compare the internal reactive process evolutions of AC modified LiNi0.6Co0.2Mn0.2O2 (NCM622) cathodes and pristine NCM622 cathodes at high C-rates. The charge transfer dynamic is revealed by the time of flight secondary ion mass spectrometry and X-ray photoelectron spectra analyzes. The addition of AC endows the NCM622 cathode regions close to the current collector possess higher lithium ion concentrations, meanwhile more Ni2+ can be converted into Ni3+. The results of COMSOL Multiphysics simulations based on the porous electrode theory is analyzed to explore reaction kinetics mechanism. AC in NCM622 cathodes homogenizes the reaction distributions, contributing to the boosted reaction kinetic, eventually, resulting in the high utilization of active materials. These findings provide a direct way to reduce solid-state diffusion resistances and accelerate reaction kinetics of electrodes, which is critical for developing batteries with long cycle stability and rate performance at high rates.

Metal sulfide heterojunction with tunable interfacial electronic structure as an efficient catalyst for lithium-oxygen batteries

The design and preparation of catalysts with excellent stability and high activity are critical to improving the performance of lithium-oxygen (Li-O2) batteries. Heterostructural catalysts have attracted wide attention due to their tunable structure and effectiveness in promoting oxygen reduction reaction and oxygen evolution reaction kinetics. In this study, CuCo2S4/CoS1.097 polymetallic sulfides were proposed as effective electrocatalysts toward oxygen electrode reactions in Li-O2 batteries. Density functional theory calculations demonstrated that the electronic structure of CuCo2S4/CoS1.097 was regulated at the heterogeneous interface, which was beneficial for optimizing the adsorption of intermediates during the reaction, eventually accelerating the sluggish kinetics of oxygen electrode reactions. The CuCo2S4/CoS1.097-based Li-O2 batteries exhibited a high specific capacity of 26,727.8 mAh g−1 and an outstanding durability of over 267 cycles at 100 mA g−1. This study provides a new perspective on the design and application of excellent cathode materials in Li-O2 batteries.

A Low‐Cost and Recyclable Mg/SOCl2 Primary Battery Via Synergistic Solvation and Kinetics Regulation

AbstractLithium/thionyl chloride (Li/SOCl2) primary batteries are appealing power solutions because of their remarkable electrochemical performances. However, their mass applications are hindered by the challenges in sustainability, cost and safety concerns owing to the employed Li chemistry. Here, magnesium (Mg) chemistry is shown as a promising alternative through synergistic optimization of electrolyte solvation and electrode reaction kinetics. The first Mg/SOCl2 primary battery yields surprisingly high specific capacities up to ≈14 000 mAh g−1 at a decent discharge voltage of ≈1.67 V, which outperforms the state‐of‐the‐art Mg‐based primary batteries. In addition, it retains almost 100% of the original capacity after 20‐day reservation. The impressive battery performances are originated from the stabilized MgCl2 formation on high‐surface‐area carbon cathode and suppressed Mg anode corrosion via the Mg‐induced solvation effect. Mg/SOCl2 primary batteries are promising candidates for low‐cost and recyclable power supplies, and they thus open new avenues for the development of sustainable battery chemistries.

Decoupled measurement and modeling of interface reaction kinetics of ion-intercalation battery electrodes

Ultrahigh rate performance of active particles used in lithium-ion battery electrodes has been revealed by single-particle measurements, which indicates a huge potential for developing high-power batteries. However, the charging/discharging behaviors of such ion-intercalation materials at ultrahigh C-rates can no longer be described by traditional electrochemical kinetics. In the meantime, regular kinetic measuring methods meet a challenge due to the coupling of interface reaction and solid-state diffusion processes, resulting in inaccurate kinetic characterizations of active particles. Here, we decouple the reaction and diffusion kinetics via time-resolved potential measurements with an interval of 1 ms, revealing that the classical Butler-Volmer equation deviates from the actual relation between current density, overpotential, and Li+ concentration. An interface ion-intercalation reaction model is developed which considers the excess driving force of Li+ (de)intercalation in the charge transfer reaction for ion-intercalation materials. Simulations demonstrate that the proposed model enables accurate prediction of charging/discharging at both particle and electrode scales for various active materials. The kinetic limitation processes from single particles to composite electrodes are systematically revealed, promoting rational designs of high-power batteries

Nanoscale nickel phosphide encapsulated in carbon microsphere from a spherical MOF toward high-performance supercapacitors

Transition metal phosphides (TMPs) are considered excellent candidate electrode materials for supercapacitors (SCs) due to their high theoretical capacity. However, the severe performance degradation of TMPs, originating from poor conductivity and resulting volumetric expansion under electrochemical conditions, hinders the practical and large-scale application in supercapacitor electrodes. Herein, a robust heterostructure of nanoscale nickel phosphide encapsulated in carbon microsphere (Ni2P @ CM) is constructed through the carbonization of spherical Ni-MOF, and followed by subsequent low-temperature phosphorylation. The MOF-derived uniform carbon layer on the Ni2P surface provides massive electron transport channels and physically restricts the volumetric expansion during electrochemical reactions, facilitating the electrode reaction kinetics and further leading to a good capacitive performance in high capacitance (1622 F/g at 1 A/g), long-term cyclic stability (75.2% capacitance retention after 8000 cycles at 20 A/g), and high rate capability. Furthermore, asymmetric SCs based on Ni2P @ CM and AC exhibit a high capacitance of 135.4 F/g at 0.5 A/g, and a remarkable energy density of 47.46 Wh/kg at a power density of 0.397 kW/kg with the excellent cyclic property. These results demonstrate that the methodology is highly promising in the design and construction of Ni2P/carbon hybrid electrodes, revealing an attractive candidate electrode material in high-property energy-storage devices.

Porous Electrode Materials for Zn-Ion Batteries: From Fabrication and Electrochemical Application

Porous materials as electrode materials have demonstrated numerous benefits for high-performance Zn-ion batteries in recent years. In brief, porous materials as positive electrodes provide distinctive features such as faster electron transport, shorter ion diffusion distance, and richer electroactive reaction sites, which improve the kinetics of positive electrode reactions and achieve higher rate capacity. On the other hand, the porous structures as negative electrodes also exhibit electrochemical properties possessing higher surface area and reducing local current density, which favors the uniform Zn deposition and restrains the dendrite formation. In view of their advantages, porous electrode materials for ZIB are expected to be extensively applied in electric and hybrid electric vehicles and portable electronic devices. In this review, we highlight the methods of synthesizing porous electrode materials and discuss the mechanism of action of porous structures as electrodes on their electrochemical properties. At the end of this review, the perspectives on the future development of porous materials in the field of electrochemical energy storage are also discussed.

Grapevine-like high entropy oxide composites boost high-performance lithium sulfur batteries as bifunctional interlayers

Lithium-sulfur batteries (LSBs) with high energy densities have been demonstrated the potential for energy-intensive demand applications. However, their commercial applicability is hampered by hysteretic electrode reaction kinetics and the shuttle effect of lithium polysulfides (LiPSs). In this work, an interlayer consisting of high-entropy metal oxide (Cu0.7Fe0.6Mn0.4Ni0.6Sn0.5)O4 grown on carbon nanofibers (HEO/CNFs) is designed for LSBs. The CNFs with highly porous networks provide transport pathways for Li+ and e−, as well as a physical sieve effect to limit LiPSs crossover. In particular, the grapevine-like HEO nanoparticles generate metal-sulfur bonds with LiPSs, efficiently anchoring active materials. The unique structure and function of the interlayer enable the LSBs with superior electrochemical performance, i.e., the high specific capacity of 1381 mAh g−1 at 0.1 C and 561 mAh g−1 at 6 C. This work presents a facile strategy for exploiting high-performance LSBs.

Methylene blue intercalated vanadium oxide with synergistic energy storage mechanism for highly efficient aqueous zinc ion batteries

With the rise of aqueous multivalent rechargeable batteries, inorganic-organic hybrid cathodes have attracted more and more attention due to the complement of each other's advantages. Herein, a strategy of designing hybrid cathode is adopted for high efficient aqueous zinc-ion batteries (AZIBs). Methylene blue (MB) intercalated vanadium oxide (HVO-MB) was synthesized through sol–gel and ion exchange method. Compared with other organic–inorganic intercalation cathode, not only can the MB intercalation enlarge the HVO interlayer spacing to improve ion mobility, but also provide coordination reactions with the Zn2+ to enhance the intrinsic electrochemical reaction kinetics of the hybrid electrode. As a key component for the cathode of AZIBs, HVO-MB contributes a specific capacity of 418 mA h g−1 at 0.1 A g−1, high rate capability (243 mA h g−1 at 5 A g−1) and extraordinary stability (88% of capacity retention after 2 000 cycles at a high current density of 5 A g−1) in 3 M Zn(CF3SO3)2 aqueous electrolyte. The electrochemical kinetics reveals HVO-MB characterized with large pseudocapacitance charge storage behavior due to the fast ion migration provided by the coordination reaction and expanded interlayer distance. Furthermore, a mixed energy storage mechanism involving Zn2+ insertion and coordination reaction is confirmed by various ex-situ characterization. Thus, this work opens up a new path for constructing the high performance cathode of AZIBs through organic-inorganic hybridization.

Effect of fluoroethylene carbonate additive on the low–temperature performance of lithium–ion batteries

• FEC increased the ionic conductivity and electrochemical stability of electrolyte. • The inclusion of FEC enables Li||LCO cell to work efficiently at −40 °C. • The production of a highly fluorinated interfacial coating can be aided by the FEC. • FEC shows the advantage of high rate discharge at low temperature. The operation of lithium–ion batteries (LIBs) at low temperature is hampered by decreased electrical conductivity and delayed electrode reaction kinetics. Due to its positive solid electrolyte interphase (SEI) formation properties, fluoroethylene carbonate (FEC) is one of the most widely researched additives for LIBs. Herein, charge–discharge tests, electrochemical impedance spectroscopy scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X–ray photoelectron spectroscopy (XPS) were used to investigate the effect of FEC on LCO/Li cells. According to SEM, TEM and XPS results, the addition of FEC results in the formation of a thin and stable cathode–electrolyte interface (CEI) film on the surface of the LCO electrode. Charge–discharge curves show that adding FEC to the electrolyte reduces polarization while increasing the discharge capacity. At −40 °C, the discharge capacity in electrolyte with 10 wt% FEC is 75.3 % that at room temperature and only 46.8 % without FEC at 1C. LiF is the main component of the FEC electrochemistry that forms a CEI, which has a low interfacial resistance and improves the ionic conductivity of the electrolyte, thus facilitating the performance of the battery at low temperature.

A Zinc-Bromine Battery with Deep Eutectic Electrolytes.

A deep eutectic solvent (DES) is an ionic liquid-analog electrolyte, newly emerging due to its low cost, easy preparation, and tunable properties. Herein, a zinc-bromine battery (ZBB) with a Zn-halide-based DES electrolyte prepared by mixing ZnBr2 , ZnCl2 , and a bromine-capturing agent is reported. The water-free DES electrolyte allows a closed-cell configuration for the ZBB owing to the prevention of Br2 evaporation and H2 evolution. It is found that the Cl- anion changes the structure of the zinc-halide complex anions and demonstrated that it improves the ion mobility and electrode reaction kinetics. The DES electrolyte with the optimized ZnCl2 composition shows much higher rate capability and a cycle life 90 times longer than that of a ZnCl2 -free DES electrolyte. A pouch-type flexible ZBB battery based on the DES electrolyte exhibits swelling-free operation for more than 120 cycles and stable operation under a folding test, suggesting its potential in consumer applications such as wearable electronics.

Electrocatalysis in Li–O2 battery over single-atom catalyst based on g-C3N4 substrate

The development of Li–O2 battery is severely hindered by the sluggish reaction kinetics of the oxygen electrode. Herein, we perform a first-principles study of single transition metal atom supported on g-C3N4 substrate (TM/g-C3N4) as potential single-atom catalyst (SAC) in Li–O2 batteries. Combined electronic analysis and thermodynamic calculations, the electrocatalytic mechanism of TM/g-C3N4 SACs in Li–O2 batteries is elucidated. Due to strong metal-substrate interactions, the TM atom is durably anchored at the unsaturated pyridine N site in the holey g-C3N4 substrate, thereby enabling long cycling stability of the oxygen electrode. Among the fifteen candidates studied, Ru/g-C3N4 SAC exhibits the lowest discharge and charge overpotentials. This behavior can be attributed to the synergistic effect of the moveable d electrons of Ru and electron-rich N coordinators, which results in significant interfacial charges, metallic electrical conductivity, and large spin magnetic moments of the RuN2 active center. This study provides in-depth atomic and electronic insights into the catalytic mechanism of TM/g-C3N4 SACs in Li-O2 batteries.